1. Field of the Invention
The present invention relates to an improvement in an engine cooling system for an outboard motor.
2. Description of the Related Art
Conventionally, an engine cooling system is known from Japanese Patent Laid-Open Publication No. HEI 3-168353 entitled "Exhaust Passage for Internal Combustion Engine".
As shown in FIGS. 2 and 4 of the publication, the disclosed engine cooling system includes a cylinder head, a cylinder block with a plurality of cylinders arranged generally horizontally in vertical juxtaposition, and a water jacket provided to surround the cylinders. An elongate second exhaust passage, opening along the cylinders, is provided at a joining surface of the cylinder block at which it is to be joined with the cylinder head. The water jacket is arranged at the joining surface of the cylinder block such that it substantially surrounds the opening of the second exhaust passage.
The known system, however, has a drawback in that no part of the water jacket is present as part of an outer wall of the second exhaust passage. The result is that the temperature of that part of the wall of the second exhaust passage temporarily rises undesirably.